premeds

Re: premeds

Siobhan Steven — Sat, 01 Jun 2013 09:41:38 GMT

Hmmm Buprenorphine isn't a very good analgesia for an OVH...when you consider it is a laparotomy with an organ being removed, we wouldn't give anything less than methadone and I also do bupivicaine local line blocks, not hard to do at all.

Glad it helps. :)

Re: premeds

Alana Dent — Sat, 01 Jun 2013 08:29:44 GMT

My mistake, I should have written 0.02mg/kg ACP. So we havent been overdoing it! (thank god!)

We do use Buprenorphine in most procedures, including bitch spays.

Very helpfull information tho! Thank you!!

Re: premeds

Siobhan Steven — Sat, 01 Jun 2013 03:44:12 GMT

Wow! Sorry that was sooo long! Just clarifying, you will get sedation from the ACP (0.02-0.03mg/kg) when given IM with the methadone, just no sedation effect from the methadone in a healthy patient at 0.5mg/kg, sometimes we will use methadone only in a patient that is compromised with no tranquillisation (no ACP or medetomidine), we may give midazolam in the compromised patient, midazolam as a premed in an uncompromised patient can increase the chance of the patient going through exaggerated 'excitation phase' if that patient is prone to it. Does that make sense...? :)

I'm assuming you are using the Buprenorphine in minor procedures as a premed...?

Re: premeds

Siobhan Steven — Sat, 01 Jun 2013 03:18:26 GMT

Some people would say its down to personal preference, some would say use the drugs you are most used to, and a lot of anaesthesia books will say the best anaesthetic to use is the one you are most used to. But from a 'desirable' side effect s 'undesirable' side effect I would personally use medetomidine over ACP in an uncompromised patient (no cardiac issues) for an ortho procedure, its a different story with, say, a moribund patient but we will stick with the ortho case...ACP contributes to vasodilation which obviousley leads to hypotension, along with Isoflurane and your induction agent (usually propofol or alfaxalone?) which also contribute to vasodilation and some degree of cardiac output compromise, therefore increasing your hypotension.

The dose of ACP you quoted (0.2mg/kg) is very high, I would usually use 0.02-0.03mg/kg coupled with the opioid of choice (methadone or hydromorphone usually, again depending on the case). If given IM the methadone dose is usually 0.5mg/kg, you won't get much (if any) sedation from that dose in an uncompromised patient, (the effect you will get from some drugs can be dependant on the status of the patient so doses and drugs need to be chosen/titrated to take that into account). Back to the ortho case :) .

With medetomidine you will usually actually get a transient hypertension, this is in response to the bradicardia it causes, after its 1st phase effects the patient is usually normotensive, leaving you to take care of analgesia rather than casing your butt trying to fix hypotension! You can sometimes get 1st or 2nd degree heart block as well, which we don't usually treat as its not a concern. And it is contraindicated to administer an anticholenergic to 'correct' the bradicardia...'

The dose of medetomidine we usually use for the healthy ortho dog would be anywhere from 4-6ug/kg IM and 2-4ug/kg IV (MUCH lower than 'on label'), having said that yesterday I gave a Rotti 10ug/kg medetomidine, 5mg/kg ketamine & 0.1mg/kg hydromorphone for pre castrate premed, however this 60kg Rotti is VERY aggressive and this premed dropped him like a sack of spuds! I didn't reverse the medetomidine in this guy as I didn't want him to have a rough ketamine recovery, so as the medetomidine wore off the ketamine was as well, at least to the point that when he could sit sternal he was just watching pink bunnies go by not pink elephants! Back to the ortho case...

We would do an epidural for hind orthos, or a 'high' epi for thoracic Sx, a bracial plexus block or RUMM block for fore limbs. You can give a loading dose of fentanyl, lidocaine and ketamine prior to starting your CRI's, we encompass these in our induction and then give a touch of induction agent if necessary for intubation. Or we induce with our usual agent and start the CRI's...the theory being by the time the patient is preped and draped on the table these drugs (in the CRI) will be at theraputic doses.

So for example we had a HBC dog two days ago, extensive pelvic fractures and scapula fracture, this dog had an epidural, local block in the scapula, CRIs of fent/lidocaine/ketamine, which were continued post Sx in ICU. What we do is practice 'multi modal' analgesia, as there is no one drug that will address all of the pain pathways, and by using a multimodal approach you can lessen the doses of each individual drug, gaining the good effects and minimising the 'bad' ones.

One of the things I like about medetomidine is it provides analgesia, really nicely, in combination with your other drugs. It is reversible, but remember if its reversed you lose the analgesic effects, as opposed to ACP which isn't reversible. The effects of ACP are l-o-n-g...16-24hrs, sure the dog gets up sooner than that but the effects are long, and as you say you are having slow recoveries but some of that may be down to your dose levels. Thats why some people call it 'chin glue'!

Remember fentanyl is out of your patients system within about 20 minutes of turning the CRI off, so you want to provide an alternative if you turn it off, we usually give 0.2mg/kg IV methadone 5-10 minutes prior to turning it off.

Hope this helps.

Re: premeds

Alana Dent — Fri, 31 May 2013 20:45:39 GMT

So Metomidine should be used over ACP to reduce hypotension? we use a lot of ACP with Methadone or Fentanyl, and do see slow recoveries in Ortho / major Op's. We as a general rule, use ACP/Methadone (0.2mg/kg and 0.3mk/kg) Premed. Ketamine and Fentanyl CRI with loading dose of Ketamine.

We always use a premed. Mostly Buprenorphine if concerned. I didnt know that it the binding process takes 30 mins plus i/v. We use i/m and induce GA after 30 mins.

I have used previously Lidocaine CRIs to help with pain. Are these any good? We dont use them currently, we use local blocks. Is there an advantage to one or other?

Re: premeds

leanne walker — Wed, 22 May 2013 16:22:46 GMT

we do use ecg and blood pressure monitoring and we see an initial drop in blood pressure but is usually back up to over 60mmhg once surgery is starting. with the recoveries we find they are really nice...they do take longer but still able to go home the same day after tta/tplo surgery, even hip replacements. our orthopaedic vet who uses these premeds has apparently taken them from what they tend to use at liverpool university. we dont tend to have any problems with our ga's so i cant imagine he would be willing to change the protocol. its more the lack of premeds completely in some of the cases i was concerned about....ie just prop dropping something for an xray etc.

Re: premeds

Siobhan Steven — Wed, 15 May 2013 09:28:24 GMT

Just to clarify,The BSAVA Small Animal Formulary 6th Edition quotes 'Propofol does not have any analgesia properties, therefore it is better used with other drugs to maintain anaesthesia'. (page 291). Amongst numerous other references that state similar and the European Boarded DVM I work with...the pain pathways will have been stimulated during surgery or even innocuous procedures like Penn Hip rads, once recovery has occurred if no other analgesia has been used (which is what the question is related to) the patient will experience pain, I am trying to clarify that neither propofol or isoflurane alone or together are adequate even for 'small procedures'.

Re: premeds

Siobhan Steven — Wed, 15 May 2013 09:13:04 GMT

Just clarifying in relation to the action/ side effects of some of these drugs. ACP can contribute to profound hypotension, medetomidine has a transient hypertensive effect and bradycardia, it also provides analgesia and can be reversed (the analgesic effects are also reversed though). Combining the two is not necessary and I would be concerned about side effects. If blood pressure and ECG monitoring is used have you seen any anomalies? You can often see 1st or 2nd degree heart block from medetomidine which doesn't need treating, usually, and as long as blood pressure is acceptable (MAP over 60mmHg) bradycardia does not need treatment (in fact it is contraindicated to use an anticholinergic, atropine or glycopyrolate, as it causes the myocardium to contract excessivly and increase O2 demand, so if these drugs are needed atipamazole should be given first if the first phase of medetomidine is still in effect.

ACP is probably what causes the longer recoveries, you can still have a very smooth recovery with just medtomidine and an opioid, with effective drug use, analgesia and protocols rough recoveries should be very rare, and 2-3 ug/kg of medetomidine, a small amount of propofol or alfaxalone or some diazapam will assist with calming the patient while Iso gets 'blown off' as this is a common cause of dysphoria in recovery, a good 10 mins of 100% O2 will assit the recovery and ensure the iso doesn't escape into the environment for you to breath.

Re: premeds

leanne walker — Mon, 13 May 2013 14:10:00 GMT

it tends to be the mix of those drugs in one patient....obviously it gets altered for certain cases...ie no or decreased acp for oap/brachycephalic breeds. we find they work really well for us....obviously have a bit of longer recovery but that works in our favour as most of our cases are orthopaedic and the last thing we want is them jumping up after a quick recovery and thrashing round the kennels. if the case is something that isnt considered that major and we arent concerned about post op thrashing around we just give acp/vet or acp/methadone.

Re: premeds

leanne walker — Mon, 13 May 2013 14:05:57 GMT

[quote user="Mark Hedberg"]

If it's that minor, I'd personally prefer the sedative option, I just don't see that there's any advantage to skipping the premed in a non-emergency case. (except in cases where clinically contraindicated, eg caesarian and so on.) I don't think it's laziness - after all, clipping a vein and intubating for GA sound like more work than a quick IM injection! :)

[/quote]yeah thats how i feel too....but i need some sort of clinical reason in order to put my case across

Re: premeds

Siobhan Steven — Sat, 11 May 2013 00:26:42 GMT

Hi Leanne,

Just wondering if you use all those drugs, ACP?Dpm?Ket?Methadone in the one patient or mix and match a combo for each patient?

Re: premeds

Paula Wright RVN Ncert (A&CC) — Thu, 09 May 2013 13:42:19 GMT

We tend to give our cesarians an I/M inj of Pethidine before surgery. Essentially its abdo surgery and Mum will feel pain - although care must be taken for the pups sake Mum is priority. Also with nitrous - having it on until just before the vet enters the uterus, off while the pups are removed (who are then usually given o2 therapy as part of reviving) then back on for spay/closure is another way to provide analgesia to an animal with minimal on board.

Re pre-meds, its essential to provide a good premedication regime for many reasons already mentioned by folk here. I prefer intravenous, and although most drugs work 'quicker' IV I have read and heard (and take into consideration) that buprenorphine takes 30 minutes whichever route it is administered (I don't bother with s/c but i/m / trans mucosal / i/v = 30mins). This is because of the binding time rather than it reaching where it needs to go.

Re: premeds

Mark Hedberg — Wed, 08 May 2013 20:51:43 GMT

Re: premeds

leanne walker — Wed, 08 May 2013 17:45:41 GMT

thankyou for all your replies. we tend to use acp/dom/ket/methadone combination for our major procedures such as TTA's or fracture repairs and acp/methadone or acp/buprenorphine for minor things. but occassionally if we are just doing a very minor procedure such as xrays or minor implant removal one of our vets suggests just 'prop - dropping' followed by iso for a 'quick' recovery. it doesnt sit easily with me as i would personally prefer a sedative such as dom/torb which is reversed and seems to be a nicer recovery but just wondered what other people think?

Re: premeds

Gillian Mostyn — Mon, 06 May 2013 22:05:33 GMT

[quote user="Siobhan Steven"]No, I meant what I said about Iso and propofol, they are not analgesics.[/quote]

I agree- they are not analgesics. However, you initially said that the animal still feels pain and is 'screaming on the inside' This gives the impression that they are like a neuromuscular blocker - where the animal simply cannot respond. In fact they are anaesthetics, so the animal has a complete, reversible loss of consciousness to all stimuli - including pain. Ensuring that the recovery is as pain free as possible is,I agree, imperative.

Re: premeds

Siobhan Steven — Mon, 06 May 2013 11:05:30 GMT

No, I meant what I said about Iso and propofol, they are not analgesics. Their actions are not fully understood, there is a thought that they act on GABA and NMDA receptors but they are both metabolised so quickly there is no longevity of any analgesic properties. The 'twisting' of the vaporiser adjustment isn't an acceptable way of preventing response to noxious stimulus.

I guess Leanne needs to elaborate on what a non painful procedure is, where Iso/propofol would be sufficient...

For C sections a local line block and/or epidural can be administered in minutes, and once the neonates are removed an opioid can be administered.

I wouldn't want to wake up in a few seconds, if it meant I experienced dysphoria but there is nothing wrong with a rapid, pain free recovery, which is what we aim for.

Re: premeds

Gillian Mostyn — Mon, 06 May 2013 08:12:14 GMT

iso/sevo and propofol do stop the animal feeling pain - they stop all sensation completely. However, I assume you mean they don't stop the body reacting to pain in a physiological way - you still get tissue swelling and damage etc. This could be reduced with the use of analgesics so there is less pain on recovery.

Also, I do agree that giving a pre-med after induction can be really useful to aid a slow and peaceful recovery. Such as a c-section, where you may have chosen not have given one pre-op, would anyone really want to go from complete GA to completely awake in a few seconds????? I wouldn't.

Re: premeds

Siobhan Steven — Sun, 05 May 2013 11:36:04 GMT

Oh, I forgot to mention, Iso and Propofol DO NOT provided analgesia, they take away the animals ability to RESPOND to pain, but not its ability to FEEL pain. So essentially, they are screaming on the inside (if that makes sense?)

I should also have said that with sufficient premedication we can intubate most of our patients on 0.5-2 mg/kg of proposal, though we draw up 6mg/kg in preparation for induction, or we can usually get away with 0.5-1 mg/kg Alfaxalone CD.

Re: premeds

Siobhan Steven — Sun, 05 May 2013 11:31:06 GMT

Oh, I forgot to mention, Iso and propofol have no analgesic properties, they only prevent the animal from responding to pain, they do not stop the patients ability to feel pain.

Re: premeds

Siobhan Steven — Sun, 05 May 2013 11:29:11 GMT

Premedication is administered for numerous reasons. The solution administered should provide a combination of analgesia and sedation/tranquilisation.

The analgesia provided should be relevant to the procedure being conducted, for example, for follow up xrays from, say, a TPLO done 6 weeks ago Butorphanol/ ACP or Butorphanol/Medetomidine can be used, for an elective desexing Butorphanol does not provide sufficient analgesia. Methadone/ ACP or Methadone/ Medetomidine could be used. For a splenectomy or porto systemic shunt a combination of premedication containing Fentanyl/ Ketamine/ Lidocaine or various other drugs could be used and then delivered as a CRI. The difference in protocols is dictated by the disease process, any contraindications due to breed predispositions, underlying problems, blood work and current medications.

If analgesia is not given prior to surgery or at such a time as it is not at theraputic levels prior to surgical 'insult' catecholamines will be released and higher doses and more potent drugs will be needed, and even then they may not have the desired effect due to 'wind up' pain, i.e once the pain pathways are open its much harder to 'close' them than it is to provide pre-emptive analgesia, and at higher doses you will get more 'undesirable' side effects vs 'desirable' side effects.

The premedication should provide sufficient sedation to allow for catheter placement and stress free handling of the patient, as, again, a stressed animal will undergo the 'stress response', where catecholamines will be released and you will be chasing your butt keeping patients at a decent level of anaesthesia.

So, by way of explanation, when I am doing an orthopeadic surgery, a TPLO for example, I will give 0.5 mg/kg methadone IM or 0.2-0.3 mg/kg methadone IV if a catheter has been placed. Medetomidine at 5-10ug/kg IM or 2-4 ug/kg IV. I tend to stay away from ACP as it causes such profound hypotension, but as I work at a university we allow students to choose drugs (under supervision) so if they choose ACP I let them if not contraindicated but can guarantee the patient will get hypotension. I will do an epidural (morphine/bupivicaine), and also run fentanyl at 0.3ug/kg/minute for the surgery. These patients will then get 0.2mg/kg methadone at the end of the surgery and Q4-6 for 24 hrs + after the surgery and a NSAID.

For a desexing the patient will get the methadone & ACP or medetomidine (and we also have hydromorphone which use in place of methadone to allow students to see the effect of this drug on many cases). They will get an NSAID at the end of Sx if no hypotension or bleeding issues, and go home on 5 days oral NSAID. You can administer a benzodiazpene (midazolam/diazapam) as this will tend to lessen the amount of induction agent needed and the amount of maintainence agent do to its protein binding properties, and also provides additional muscle relaxation.

I've just read through all of this, sorry its so longwinded but it is a huge topic which I am passionate about, I found that when I had developed a good understanding of the pain process, pathways and neuro-muscular system I had a lot more respect for the whole premed/analgesia/anaestheic topic, now its my full time job my aim is to never have a patient who is uncomfortable or experiencing pain.

If I can be of any further help please ask. :)

Re: premeds

Julie-Anne Wilson — Sat, 04 May 2013 23:17:24 GMT

The only time I've seen a pre med NOT used is a caesarian and I think that's so the mum and babies wake up quicker. Other than that, always a pre med with propofol and gas

Re: premeds

bongo — Thu, 02 May 2013 15:33:16 GMT

yeah I would be a bit dubious about post induction pre med as pre meds are supposed to lower the amount of induction needed and also make for a smooth induction - two reasons out of many to pre med! The only time I have ever not seen one given is with emergency c sections. Where I am now we always give one, no matter what the case, even if its an emergency there is always something you can give and if given I/v it pretty much works instantly!

Re: premeds

Mark Hedberg — Thu, 02 May 2013 10:39:03 GMT

A premed doesn't just calm the animal, it can reduce the amount of anaesthetic agent you use; and it's a good goal to use as little as possible to effect. So an unpremedicated animal may need 10ml of propofol to go to sleep, and a premedicated animal may only need 4ml. Lower drug amounts decrease the likelihood of side effects; and having a relaxed and calm animal in your prep room is nicer than having a potentially nervous pet in there. An animal that is on a lower rate of iso will likely have a faster recovery as there's less gas to get out of the system, so to speak.

When considering only sedatives, tranquilizers, opioids, this is a good summary:

1. Premeds will decrease the amount of drugs you use, lowering the likelihood of side effects

2. You are likely to have a faster induction

3. You are likely to have a smoother, more stable state of anaesthesia

4. Because of this and the lower amount of anaesthetic drug, you will likely have a faster recovery after surgery.

Post-induction pre-med I'm not convinced of the benefits of, but I speak as an ex-first opinion practitioner and not an anaesthetic expert.

Good luck!